Microphone



O. ANGELINI MICROPHONE May a, 1924. 13493415 Filed Dec. 31 1919 WITNESSES- INVENTOR Kama/$22M. oresafilg'elw ATTORNEYS case.

Patented May 6, 1924.

UNITED STATES OBES'IE ANGELINI, OF ROME, ITALY.

MICROPHONE.

Application filed December 31,1919. Serial 'No; 348,712.

(GRANTED UNDER T E rnovrsrons on THE ACT or MARCH 3, 1921,41 s'rA'L L, 1313.

To all whom it may concern:

Be it known that I, Onns'rn ANGELINI, a subject of the King of Italy, and resident of Rome, Italy, have invented certain new and useful Improvements in or Relating to Microphones (for which I have filed applications in Italy, filed Dec. 2, 1915, Reg. Gen. No. 151603 and patent of addition in Italy, filed Jan. 18, 1916, Reg, Gen. 152376), of which the following is a specification.

My invention relates to improvements in with the diaphragm removed,

Figure 2 is a section on line 22 of Figure 1 and showing the diaphragm. Referring to the drawing, A is a case composed of hard insulating material provided with two grooves or channels 1 and 2,

separated by a partition a, which projects beyond one end of the case. 3 and 5 are electrodes at the ends of the grooves or channels 1 and 2, respectively, and between which the partition (6 projects. 1 is a metal plate at the other end of the case and forming an end wall for the grooves or channels. 6 is the mass of carbon granules in the grooves or channels of the case, and 7 is a vibrating diaphragm of non-conducting material arranged a short distance above the The electric current flows from electrode 3 through the carbon granules in channel 1, to plate 4:, then through the carbon granules in channel 2 to the electrodes 5. The surface of the plate 4 contacting with thecarbon granules is parallel to the surface of the electrodes 3 and 5, which also contacts with the carbon granules.

The purpose of the microphone'to which the present invention refers, is the utilization of the great variations of the conductivity that the vibrations of the diaphragm '7 produce through the strip of grains of carbon, which receives upon its full length the pressure variations transmitted by the diaphragm. Q i

It is thus that the variations of the resistance of the strip is very considerable, said variations may efiicaciously influence strong external resistances, that is to say the resistance of a line.

It may be that the current, flowing through the wire of an aerial line of a cable systemthus obtainedmay be only a pulsat ing current, greatly reducing the efiects due I to the impedance of the aerial wires and to the capacity of the cables, because the impedance, the autoinduction and the capacity Wlll have a lesser influence on the pulsating current sent by the microphone than on the alternate currents generated through the usual microphones through the secondary of their transformers, also if the alternate currents have a frequency double of the pulsation of the current. As it may be desired that the pulsating current shall not act di-- rectly on the telephone receiver of the receiving station, this station may be provided with a suitable transformer; of which the primary is connected to the line and the secondary to the receiver and vice versa.

Various changes and modifications may be made to the arrangement and construct1on of the invention herein described withp out departmg from the spirit ofthe invention.

What I claim is:

A microphone comprising a case of hard insulating material provided with two grooves or channels filled with carbon granules, electrodes at one end' of the case, one

for each groove or channel and insulated from one another, a metal plate at the other end of the case and forming an end wall for the said grooves or channels, parallel with the electrodes, and a vibrating diaphragm of non-conducting material above and in close proximity to the case.

In testimony whereof I have hereunto signed my name in the presence of two wit-i nesses:

ORESTE ANGELINI.

Witnesses:

DoARLo AsooLI, DELLA; Z. ZoooLo. 

